Just purchased new light - should I replace bulb

This is a discussion on Just purchased new light - should I replace bulb within the Beginner Planted Aquarium forums, part of the Beginner Freshwater Aquarium category; -->
I just bought a Coralife Aqualight 30&quot; Dual lamp T5 2x18w. For my 30g planted tank. I currently have Anubias, Java Fern, Anacharis, Wisteria, ...

The tubes are fine, with respect to spectrum. I would be more concerned over the increased intensity, especially if the plants were doing well previously. Now that the light is significantly greater, the nutrients are not, esp CO2. Reducing the light duration may be necessary. Keep a close eye on the tank, looking out for any increase in algae which would be a sign that the light is too much.

You were right. I now have brownish/black algae growing on the tank, plants, and decorations. I can get it off with a scraper on the glass - It comes off of some plants by rubbing but on others it doesn't.

My ammonia and nitrites are 0. My nitrate is 40ppm. I am going to do a water change now to try to bring that down. My last water change was a 20% yesterday so the high nitrates are alarming.

I have been dosing with half a cap full of flourish twice weekly. My lights are on for about 9 hrs a day.

Outside of reducing my lighting period - any steps to take? What should I start my lighting period at now?

You were right. I now have brownish/black algae growing on the tank, plants, and decorations. I can get it off with a scraper on the glass - It comes off of some plants by rubbing but on others it doesn't.

My ammonia and nitrites are 0. My nitrate is 40ppm. I am going to do a water change now to try to bring that down. My last water change was a 20% yesterday so the high nitrates are alarming.

I have been dosing with half a cap full of flourish twice weekly. My lights are on for about 9 hrs a day.

Outside of reducing my lighting period - any steps to take? What should I start my lighting period at now?

Sounds like Black Brush Algae, or Red Brush Algae. It is actually a red algae but to most of us it appears very dark green or more black. Light is the cause. Reduce your duration by an hour and see if it stops increasing. What is there now wll not go away, but if it stops increasing, fine. If reducing one hours doesn't stop it, reduce another hour. You have to find the balance between light and the available nutrients. And CO2 is the one that is natural and often the one that gives out first. The light has to be the limiting factor.

On the nitrates, that is high for a planted tank. Is this tank fairly new?

I thought it was high too. Tank was setup in June. Plants added slowly since July.

I changed the timer to a 8hr schedule. I am assuming a week should be good to see if it halts the algae growth?

Will MTS eat this type of algae?

MTS meaning Malaysian Livebearing snails, then no; they (like all snails) graze on algae minimally but can't handle it when it is this rampant. None of the so-called algae-eating fish will touch it either, except two but they are both not advisable except in specific setups as they get large. Brush algae has to be controlled by balancing light and nutrients so the plants use them.

You might see a change in a week, or certainly two. Again, it is just noticing no increase, or very little increase, in the algae. I never bother this on wood or rock, it looks very natural; it is when I see it on plants that I take action. A bit is OK, you cannot keep the tank free of algae. You aim for the balance to keep it under control.

I asked about the new tank because in a new tank for the first say 2-3 months, the biology is settling into a balanced state and algae being quick to take advantage can often appear during this period. Once the tank is biologically stable, it is easier to then balance the light and nutrients for the plants. Algae will be out of luck then. You'll still see it, as I say, but not excessively--unless something upsets the balance. I have had brush algae suddenly increase in summer when the days are longer and brighter, just from the additional ambient light in the room. I've also had it increase when the tubes over the tank were no longer emitting sufficient intensity, which is usually after 12 months with T8, T5 should be a bit longer.